Cylindrical cutting elements are often mounted to a variety of driven elements to perform excavations of various difficult type of ground, including compacted sands, clay, gravel and rock. The driven elements include drums and chains. FIGS. 1–4 illustrate a prior art trencher 100 with a typical roller chain assembly 10. FIG. 1 illustrates the trencher 100 with a boom 102 in a raised position, and a lowered position. In the lowered position, the boom 102 forces the roller chain assembly 10 into engagement with the ground. The chain is powered by a drive sprocket, not shown, such that end idler 104 will rotate clockwise, and the bottom strand of the roller chain assembly 10 will move from right to left. When in engagement with the ground the chain assembly 10 will excavate and transport cuttings to a discharge conveyor 106, thus forming a trench as the trencher 100 moves from right to left. FIG. 2 illustrates a typical roller chain assembly 10 comprising attachment links 12, side links 14, and rollers 16. The chain assembly 10 further comprises base plates 18, conical cutters 20, tool holders 22 and back bend bars 24, as illustrated in FIGS. 3 and 4. FIG. 3 illustrates a double chain assembly where the base plates are each attached to 2 chains. The conical cutters 20 are positioned on the base plates at an angle such that they contact the ground at the required orientation. The chain assembly 10 will move from left to right as illustrated in FIG. 4, with the conical cutter 20 contacting the ground. This contact will generate an excavation force F1 on the tip of the conical cutter 20A. Conical cutter 20A is mounted to baseplate 18A which is mounted to attachment links 12A. The force F1 will generate a moment, substantially around axis 13. The chain assembly 10 will flex until backbend bars 24A contact side links 14A. In this manner the back bend bars 24 stiffen the chain assembly 10.
When utilized in extreme conditions this type of drive and mounting arrangement is has been found to be insufficient. There are times that the tool holders 22 are not sufficiently attached to the base plates and that the overall chain assembly includes sufficient flexibility to induce unwanted vibrations.
An improved mounting arrangement is needed for application of this type of excavation assembly in extreme conditions.